Take a look at this (mostly complete) list of industries, courtesy of Monster.com:

Accounting

Advertising

Aerospace and Defense

Agriculture/Forestry

Architectural and Design

Automotive and Parts Manufacturing

Automotive Sales

Banking

Biotechnology/Pharmaceuticals

Broadcasting, Music and Film

Business Services

Computer Hardware

Computer Software

Computer/IT Services

Construction

Education

Energy and Utilities

Entertainment Venues

Financial Services

Food and Beverage Production

Government and Military

Healthcare Services

Hotels and Lodging

Insurance

Internet Services

Law Enforcement

Legal Services

Metals and Minerals

Nonprofit Charitable Org

Performing and Fine Arts

Personal and Household Services

Printing and Publishing

Real Estate/Property Management

Rental Services

Restaurant/Food Services

Retail

Security and Surveillance

Sports and Physical Recreation

Staffing/Employment Agencies

Telecommunications Services

Transport and Storage

Travel

Waste Management

Trade/Import-Export

Do you see any industry in that list that would not require interaction with people? And since this list encompasses pretty much all the jobs that are out there, can you, therefore, think of any job that would not involve interaction with people? Dealing with their moods and idiosyncrasies, understanding them, relating to them and spending time with them? There are probably a few non-people jobs out there, but the percentage is incredibly low.

Your job/career is one of the places where you’ll see Biggie #3 surface really fast. It’s all about other people and how you interact with, deal with, and treat them. An incomplete list or reasons:

It’s a widely accepted fact that likable people, i.e. people who are easy to relate to, do better in their jobs; books have been written about increasing your likeability

In Trent’s excellent article about getting ahead at work, 10 out of 14 tactics have to do with relating to others

If you’re difficult to deal with, the only way you’re staying around is if you are skilled in your craft or, if you’re well connected (once again, relationships! 😉 ). But people will dislike you, and will simply put up with you. If you have worked for any length of time, you probably know a person like that.

It’s hard to achieve anything but the bare minimum if you don’t have the trust or support of your boss or coworkers

Understanding the people you’re interacting with helps you “speak their language” – multiple tests like the DiSC Profile and Myers-Briggs Type Indicator are used by companies to help their employees understand how to better interact with one another

People have feelings, moods, and ups and downs; the better you can read these, the better off you’ll be

#6 requires a bit of an elaboration:

So much talking is done about the “real world” and “being professional,” while we’re in school or just starting out, that we get caught in the trap of formulaic approach to people at work: show up at your cubicle, submit your report to the boss, answer a co-worker’s email, host a meeting, go home. Co-workers and bosses are just other chess pieces, moving around the chessboard. We tend to forget that every single person around us carries with them happiness or sadness or excitement or gloominess, and all of the baggage (good and bad) from the non-work hours gets hauled into the office every day. Likewise, there are bad and good days, for a multitude of reasons. Sometimes, the mood of a person or a whole group is relaxed, and other times, you get a sense that just one more straw will break the proverbial camel’s back.

As such, there are times to joke, and there are times to remain somber and business-like. There are times to pull people aside and check in with them, and there are times to just get out of their way. There are times when playing with whatever toy you got at Thinkgeek.com will be considered hilarious, and there are times when it will get you an appointment with HR. No matter how professional people try to be, they are still people. If you learn to be attuned to how they’re feeling or to read their mood, you will be much better equipped to deal with them.

In summary, to have a meaningful job, to create a great reputation, and to have achievements that are above basic expectations, you need to be able to relate to and deal with others well. Reading Dale Carnegie’s How to Win Friends and Influence People is a great first step. To paraphrase a song once again, “there’s no people like ‘people’ people.”